The present invention relates to a composite electroplating bath to deposit a composite nickel plate composed of a nickel alloy matrix and eutectoid particles dispersed in the matrix on the metal surface.
The composite plating bath is desired to deposit a composite plate in which the particles are effective to improve the plate in physical properties. Such a bath has been disclosed by JP B 56-18080 that is prepared by adding a water soluble addition agent containing phosphorus compounds by an amount of 0.1-4.2 grams/liter to a usual nickel electroplating bath including eutectoid particles.
The bath, as disclosed above, coats the metal surface with a composite plate composed of a nickel-phosphorus alloy matrix and eutectoid particles of alumina, silicon and/or nitride dispersed in the matrix. The plate is superior in hardness and anti-abrasion properties to the conventional plate obtained from the usual bath without the phosphorus agent. However, it is still insufficient as a plate covering a slidable member subjected in service to a high load at high temperatures, such as a piston ring for use in an internal combustion engine. The member or piston ring, when plated in the aforementioned bath, is somewhat unreliable in hardness and anti-abrasion without the anti-abrasion without the help of a proper heat-treatment.